Heretofore, in this type of the image processing apparatus, an image with a gradation, such as photograph, is dither processed into 2-level image data of black and white. The image data are stored into image files, for example. A number of dots allowed for displaying on the CRT display is much smaller than that of the original image. For obtaining an appropriate display of the original image on the CRT display, therefore, the original image must be reduced in size.
The method to reduce the dither processed original image, which has been most widely employed, is to thin out the dots of the original image according to a reduction rate.
When this method to simply thin out the dots of the original image is applied to the size reduction of the original image, the dither structure of the original image is distorted, so that a resemblance between the reduced image and the original image is greatly damaged and one cannot recognize the original image when seeing the displayed image. In this respect, this thin-out method has been impractical in use.